Conveyor including an endless flexible conveying element and a tensioning device for the conveying element

ABSTRACT

A conveyor comprises an endless, flexible conveying element, a drive unit for driving the conveying element, a deflecting unit for reversing direction of movement of the conveying element, and at least one tensioning device. The tensioning device includes a displaceable tensioning element engaging the conveying element, a tensioning spring biasing the tensioning element toward the conveying element, and a unidirectional blocking mechanism which blocks a displacing movement of the tensioning element in a direction opposite the effective direction of the tensioning spring for automatic readjustment of the conveying element while maintaining the possibility of the reversing operation. The blocking action of the blocking mechanism can be cancelled by an unlocking key, and the tensioning device can be slid back into a locking position to allow the disassembly of the conveying element.

BACKGROUND OF THE INVENTION

The invention relates to a conveyor comprising an endless, flexibleconveying element, such as a conveyor belt or chain, or the like.

Such endless conveyors, also called conveyor or assembly belts, areused, depending on their purpose of application, for conveying bulk orpiece goods, or for transporting workpieces which are generally held ona pallet.

In a known endless conveyor of this type with elastic conveyor belt(DE-OS No. 33 06 079), the tensioning device with conveyor belt guiderequired for keeping the endless conveyor belt tight, is constructed asa tensioning roller which is arranged in the drive station between twosynchronously driven deflecting rollers. The axle of the tensioningroller is provided with two adjustable bearings which can be adjustedradially by two tensioning screws arranged laterally at the bearingframe, so that the tensioning of the conveyor belt can be readjustedmanually from time to time.

SUMMARY OF THE INVENTION

The object of the invention is a conveyor comprising an endless flexibleconveying element tensioning of which is maintained automaticallywithout the necessity of re-tensioning over time. The reversingoperation of the conveyor is ensured by the blocking mechanism of thetensioning device, which blocking mechanism acts on one side and is onlyeffective in a direction which is opposite the tensioning direction.When the conveying element is driven in a reverse operation, theblocking device prevents the tensioning spring from being compressed bythe tractive force of the drive. The conveying element tension lastadjusted prior to the beginning of the reversing operation is maintainedso as to be unchanged. If the conveyor is driven exclusively inreversing operation, the automatic re-tensioning of the conveyingelement is effected in the turned-off phases of the conveyor.

In an advantageous embodiment of the invention, the blocking mechanismcomprises a manually actuated unlocking key for cancelling the blockingaction of the mechanism. The key is used for slackening of the conveyingelement for assembly purposes. A lock which can be triggered as desiredin the rear end position of the tensioning member when the tensioningspring is extensively compressed, which can be realized in a simplemanner, e.g. by providing a locking groove at the end of a tooth row ofthe blocking mechanism in which groove a locking projection that can belifted only by actuation of the unlocking key, is received ensures aneasy assembly and disassembly of the conveying element when thetensioning member is installed without disassembling it beforehand.

The present invention both as to its construction so to its mode ofoperation, together with additional objects and advantages thereof, willbe best understood from the following detailed description of preferredembodiments with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic partial side view of a conveyor according tothe invention with an endless conveyor chain;

FIG. 2 shows a sectional view of a tensioning device along line II--IIin FIG. 1;

FIG. 3 shows a section of the tensioning device according to lineIII--III in FIG. 1; and

FIG. 4 shows an enlarged cross-sectional view along line IV--IV in FIG.3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The chain conveyor shown schematically in FIG. 1, comprises an endlessconveying chain 10 which is driven in the direction indicated by arrowsin the normal operation of the conveyor by a drive 11 comprising atoothed roller or toothed wheel driven electromechanically. The drive 11is combined together with a tensioning device 12 for the conveying chain10 in a drive station 13. A lower portion 101 (return portion) of theconveying chain 10 runs from the drive station 13 to a deflecting roller14, and an upper portion 102 (pulling portion) of the conveying chain 10serving to transport runs back to the drive station 13 again from thedeflection roller 14. In the drive station 13, the upper chain portion102 is guided in a track rail 15 and is guided to the drive 11 via adeflecting portion 16. The tensioning device 12 is arranged in the lowerportion 101 of the conveying chain 10, that is, between the drive 11 andthe deflecting portion 16, wherein the conveying chain 10 runs along aguide 17 of the transporting device 12. The tensioning device 12 withguide 17 acts on the conveying chain 10 in such a way that the loopingangle of the conveying chain on the conveying chain guide 17 is smallerthan 180° , and the looping angle of the conveying chain 10 at thetoothed roller or the toothed wheel of the drive 11 is greater than 180°. The tensioning device 12 is combined with the track rail 15 and thedeflecting portion 16 to form a constructional unit which is generallydesignated as a chain tightener. As can be seen from FIGS. 1 and 3, thetrack rail 15 and the deflecting portion 16 are arranged on the upperside of a section housing 18 so as to form one piece with the latter,while the tensioning device 12 is arranged in the interior of thesection housing 18.

The tensioning device 12 comprises in particular a displaceabletensioning element 19 which carries the conveying chain guide 17 on itsfront side, a tensioning spring 20 which acts upon the tensioningelement 19 in the direction of the conveying chain guide 17, and ablocking mechanism 21 which acts in one direction only in the manner ofa ratchet coupling and blocks a displacing movement of the tensioningelement 19 in a direction opposite the acting direction of thetensioning spring 20. The action of the blocking mechanism 21 can becanceled manually by an unlocking or releasing key 22 (FIGS. 2 and 3).As can be seen particularly from FIGS. 2 and 3, the tensioning element19 is constructed as a carriage 23 which is longitudinally displaceablein longitudinal guides 24, 25 arranged in the two side legs 181, 182 ofthe section housing 18. A tooth row 27, 28 is arranged above and belowthe longitudinal guide 24. Each tooth row 27, 28 extends along theentire displacement path of the carriage 23. Although this can not beseen in particular, each tooth of the tooth rows 27, 28 comprises alateral side having a profile of a sawtooth and which is directedtransversely relative to the displacement direction of the carriage 23and extends in the tensioning direction of the carriage 23, that is, inthe direction of the conveying chain guide 17, at an acute angle to thedisplacement direction of the carriage 23.

The carriage 23 comprises a recess 29 on its lateral surface 231 facingthe tooth rows 27, 28 and the longitudinal guide 24. The releasing key22 has a T-section with a middle portion 30 which projects through thelongitudinal guide 24 and is provided with a blind hole 31 and with aflat transverse web 32. On both sides of the middle portion 30, thetransverse web 32 carries locking projections 33 and 34 on the surfacesfacing the tooth rows 27, 28. A helical pressure spring 35 lies in theblind hole 31 and is supported at the base of the blind hole 31 on theone hand, and at the carriage 23 on the other hand, and accordinglypresses the locking projections 33, 34 into the tooth rows 27, 28. Thetooth rows 27, 28 and the releasing key 22 with locking projections 33,34 and pressure spring 35 form the blocking mechanism 21 with theunlocking key mentioned above. A locking groove 36 and 37, respectively,is provided at the end of the each tooth row 27, 28. Although it can notbe seen in more detail, the locking groove 36 and 37, respectively,comprises two parallel groove flanks extending transversely relative tothe displacing direction of the carriage 23. If the locking projections33, 34 catch in the assigned locking grooves 36, 37, this lockingposition of the carriage 23 can only be canceled by actuating thereleasing key 22.

The carriage 23 comprises an axial blind hole 38 in which the tensioningspring 20, which is constructed as a cylinder spring, projects and issupported at the base. The other end of the tensioning spring 20encloses a retaining pin 39 which is aligned with the pocket bore holeand is supported on a collar 40 provided at the retaining pin 39. Theretaining pin 39 is held in the rear of the section housing 18. Thecarriage 23 is pushed in the tensioning direction of the conveying chain10 by the action of the tensioning spring 20, wherein the conveyingchain guide 17 presses against the conveying chain 10. The sawtooth-liketooth shape of the tooth rows 27, 28 allows the carriage 23 to slide inthe tensioning direction when the locking projections 33, 34 engage inthe tooth rows, but prevents the carriage 23 from sliding back when aforce is exerted on the conveying chain guide 17 opposite the effectivedirection of the tensioning spring 20. Accordingly, the reversingoperation of the conveyor is possible without the action of thetensioning device 12 being canceled. In the reversing operation thereturn portion 101 of the belt and the pulling portion 102 of the belt,respectively, move in the opposite direction relative to the arrowsshown in FIG. 1.

In order to disassemble the conveying chain 10, the tensioning device 12can be taken out of operation in a simple manner by the releasing key22. For this purpose, the releasing key 22 is to be pressed in so thatthe locking projections 33, 34 are lifted out of the teeth of the toothrows 27, 28, and the action of the blocking mechanism 21 is accordinglycanceled. The carriage 23 can be slid back until its locking position atthe end of the tooth rows 27, 28 accompanied by the compression of thetensioning spring 20 when the releasing key 22 is pressed in. If thereleasing key 22 is released again in this locking position, the twolocking projections 33, 34 catch in the locking grooves 36, 37 arrangedat the end of the tooth rows 27, 28. The tensioning device 12 isreliably locked in its ineffective position. The conveying chain 10 cannow be exchanged, or other work can be performed out on it. In order toput the conveyor in operation, the releasing key 22 must be pressedagain, so that the locking projections 33, 34 are lifted out of thelocking grooves 36, 37 and the carriage 23 is displaced by the action ofthe tensioning spring 20 until the conveying chain 10 has again reachedits operating tension.

The invention is not limited to the described chain conveyor. Thetensioning device, according to the invention, can be used in the samemanner in conveyors with endless flexible conveyor belts or withcircular cord. Instead of the simple deflecting roller 14, a deflectingstation is often provided which is constructed identically to the drivestation with the single exception that the drive motor for the sprocketwheel of the drive 11 is omitted.

While the invention has been illustrated and described as embodied in aconveyor, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.
 1. A conveyor comprising an endless flexible conveying element; means for driving said conveying element; means for reversing a direction of movement of said conveying element; and at least one means for tensioning said conveying element, said tensioning means including a housing having opposite side walls, each of said opposite side walls having a longitudinal inner edge; a tensioning element engaging the conveying element and formed as a carriage displaceable between said opposite side walls; a tension spring for biasing said tensioning element into engagement with said conveying element; and a unidirectional blocking mechanism including a first group of stationary locking teeth formed in said housing and a second group of locking teeth connected with said carriage for joint displacement therewith, each tooth of said first and second groups of teeth having a lateral side which extends transverse to a direction of displacement of said carriage at an acute angle to a tensioning direction of said carriage, and a manual unlocking key supported on said carriage and carrying said second group of locking teeth, said manual unlocking key being laterally movable relative to a displacement direction of said carriage; one of said side walls defining a longitudinal guide having an opening, said tensioning device further comprising a pressure spring supported in said carriage for biasing said unlocking key in a direction transverse to the displacement direction of said carriage outward through said opening in said longitudinal guide; said first group of locking teeth including two laterally spaced rows of locking teeth formed on the inner longitudinal edge of said one side wall, said carriage having a side surface facing said two rows of locking teeth of said first group of locking teeth, and a recess, said unlocking key having a transverse web engaged in said recess, and said second group of locking teeth comprising at least two spaced locking teeth formed on said transverse web for engaging said two rows of locking teeth of said first group of locking teeth, respectively.
 2. A conveyor according to claim 1, wherein said unlocking key has a central portion having a blind hole for receiving said pressure spring.
 3. A conveyor according to claim 1, wherein said blocking mechanism includes two locking grooves at rear ends of said two rows of locking teeth remote from said conveying element for receiving said two locking teeth, said locking teeth disengaging from said grooves in response to actuation of said unlocking key.
 4. A conveyor according to claim 1, wherein said tensioning element is positioned in a conveying path of said conveying element and has a looping angle with said conveying element less than 180° , said conveyor further comprising an additional deflection element that forms with said tensioning element an integral unit.
 5. A conveyor according to claim 4, wherein said tensioning means is located between said additional deflection element and said driving means, said driving means has a looping angle with said conveying element greater than 180°.
 6. A conveyor according to claim 1, wherein said tensioning element has an end engaging said conveying element, and a guide at said end for said conveying element.
 7. A conveyor according to claim 1, wherein said conveying element has a return portion extending between said driving means and said reversing means, said tensioning device being arranged in said return portion.
 8. A conveyor according to claim 1, wherein said conveying element comprises one of conveyor chain, conveyor belt, circular cord and the like. 